[PATCH 0/4] power: supply: add battery driver for netronix ec

[PATCH 0/4] power: supply: add battery driver for netronix ec

[Josua Mayer]

This series adds a new battery driver for the netronix embedded
controller multi-function device.

Bindings are updated supporting a monitored battery, and battery
description is added to kobo aura device-tree.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
Changes in v2:
- Fixed identity mixup between from address and SoB.
  (Reported-by: Krzysztof Kozlowski <krzk@kernel.org>)
- Changed patch ordering, device-tree first.
- Separated new driver and mfd subdevice changes into separate patches.
  (Reported-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>)
- reworded Kconfig to explicitly mention device-tree
  instead of vague firmware tables expression.
  (Reported-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>)

---
Josua Mayer (4):
      dt-bindings: mfd: netronix,ntxec: add reference to power-supply
      ARM: dts: imx: imx50-kobo-aura: add description for battery
      power: supply: add battery driver for netronix ec
      mfd: ntxec: register battery subdevice.

 .../devicetree/bindings/mfd/netronix,ntxec.yaml    |   9 +-
 arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts      |   9 ++
 drivers/mfd/ntxec.c                                |   1 +
 drivers/power/supply/Kconfig                       |   9 ++
 drivers/power/supply/Makefile                      |   1 +
 drivers/power/supply/ntxec-battery.c               | 101 +++++++++++++++++++++
 6 files changed, 127 insertions(+), 3 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251227-kobo-aura-battery-3e60bc159d16

Best regards,
-- 
Josua Mayer <josua.mayer@jm0.eu>

[PATCH 1/4] dt-bindings: mfd: netronix,ntxec: add reference to power-supply

[Josua Mayer]

The Netronix Embedded Controller supports monitoring of battery voltage.

Voltage monitoring functionality is self-contained and requires no
supply- or battery-specific runtime configuration.

Battery design characteristics (e.g. voltage-min-design-microvolt) are
useful for users to understand the charge level and are commonly
provided by a separate battery node linked with monitored-battery
property.

Add reference to power-supply.yaml so that power-supplies and
monitored-battery properties become available.

Further drop reg property description and replace it with maxItems 1 as
is common for i2c devices with single bus address.

Finally replace additionalProperties with unevaluatedProperties to
allow properties from referenced schemas.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
index 37fbb953ea12..6599dcf0eceb 100644
--- a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
+++ b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
@@ -13,13 +13,15 @@ description: |
   This EC is found in e-book readers of multiple brands (e.g. Kobo, Tolino), and
   is typically implemented as a TI MSP430 microcontroller.
 
+allOf:
+  - $ref: /schemas/power/supply/power-supply.yaml
+
 properties:
   compatible:
     const: netronix,ntxec
 
   reg:
-    items:
-      - description: The I2C address of the EC
+    maxItems: 1
 
   system-power-controller:
     type: boolean
@@ -42,7 +44,7 @@ required:
   - compatible
   - reg
 
-additionalProperties: false
+unevaluatedProperties: false
 
 examples:
   - |
@@ -61,5 +63,6 @@ examples:
                 interrupt-parent = <&gpio4>;
                 interrupts = <11 IRQ_TYPE_EDGE_FALLING>;
                 #pwm-cells = <2>;
+                monitored-battery = <&battery>;
         };
     };

-- 
2.43.0

Re: [PATCH 1/4] dt-bindings: mfd: netronix,ntxec: add reference to power-supply

[Krzysztof Kozlowski]

On Fri, Jan 02, 2026 at 07:00:30PM +0100, Josua Mayer wrote:
> The Netronix Embedded Controller supports monitoring of battery voltage.
> 
> Voltage monitoring functionality is self-contained and requires no
> supply- or battery-specific runtime configuration.
> 
> Battery design characteristics (e.g. voltage-min-design-microvolt) are
> useful for users to understand the charge level and are commonly
> provided by a separate battery node linked with monitored-battery
> property.

b4 diff '20260102-kobo-aura-battery-v1-1-501f2a8fa575@jm0.eu'
Breaking thread to remove parents of 20260102-kobo-aura-battery-v1-0-501f2a8fa575@jm0.eu
---
Analyzing 6 messages in the thread
Could not find lower series to compare against.


Make it easier for us to review, not more difficult.

> 
> Add reference to power-supply.yaml so that power-supplies and
> monitored-battery properties become available.
> 
> Further drop reg property description and replace it with maxItems 1 as
> is common for i2c devices with single bus address.
> 
> Finally replace additionalProperties with unevaluatedProperties to
> allow properties from referenced schemas.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof

[PATCH 2/4] ARM: dts: imx: imx50-kobo-aura: add description for battery

[Josua Mayer]

Kobo Aura has a rechargable battery that is monitored by the embedded
controller.

Battery markings: PR-285083 3.7V Typ. 1500mAh; 575327416288 5.55Wh.

Add description for this battery and link it for monitoring by the
embedded controller.

Reviewed-by: J. Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts b/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
index b1a6a9c58ac3..dc8d9fd45cd2 100644
--- a/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
+++ b/arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts
@@ -16,6 +16,14 @@ chosen {
 		stdout-path = "serial1:115200n8";
 	};
 
+	battery: battery {
+		compatible = "simple-battery";
+		voltage-min-design-microvolt = <3400000>;
+		voltage-max-design-microvolt = <4100000>;
+		energy-full-design-microwatt-hours = <5550000>;
+		charge-full-design-microamp-hours = <1500000>;
+	};
+
 	memory@70000000 {
 		device_type = "memory";
 		reg = <0x70000000 0x10000000>;
@@ -151,6 +159,7 @@ embedded-controller@43 {
 		system-power-controller;
 		interrupts-extended = <&gpio4 11 IRQ_TYPE_EDGE_FALLING>;
 		#pwm-cells = <2>;
+		monitored-battery = <&battery>;
 	};
 };
 

-- 
2.43.0

[PATCH 3/4] power: supply: add battery driver for netronix ec

[Josua Mayer]

Implement a simple battery driver for monitoring voltage with the
netronix embedded controller found in certain ebook readers.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 drivers/power/supply/Kconfig         |   9 ++++
 drivers/power/supply/Makefile        |   1 +
 drivers/power/supply/ntxec-battery.c | 101 +++++++++++++++++++++++++++++++++++
 3 files changed, 111 insertions(+)

diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index 92f9f7aae92f..0f944c10e50b 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -1132,4 +1132,13 @@ config FUEL_GAUGE_MM8013
 	  the state of charge, temperature, cycle count, actual and design
 	  capacity, etc.
 
+config BATTERY_NTXEC
+	tristate "Battery driver for Netronix embedded controller"
+	depends on MFD_NTXEC
+	help
+	  Say yes here to enable netronix ec battery monitoring driver.
+	  It enables the monitoring battery voltage on certain e-book readers
+	  using an embedded controller by ODM Netronix. Battery design
+	  characteristics are read from device-tree if available.
+
 endif # POWER_SUPPLY
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 4b79d5abc49a..db6fc815f9da 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
 obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
 obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
 obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
+obj-$(CONFIG_BATTERY_NTXEC)	+= ntxec-battery.o
diff --git a/drivers/power/supply/ntxec-battery.c b/drivers/power/supply/ntxec-battery.c
new file mode 100644
index 000000000000..f49f0966d18d
--- /dev/null
+++ b/drivers/power/supply/ntxec-battery.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The Netronix embedded controller is a microcontroller found in some
+ * e-book readers designed by the original design manufacturer Netronix, Inc.
+ * It contains RTC, battery monitoring, system power management, and PWM
+ * functionality.
+ *
+ * This driver implements battery monitoring.
+ *
+ * Copyright 2021 Josua Mayer <josua.mayer@jm0.eu>
+ */
+
+#include <linux/mfd/ntxec.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+static const enum power_supply_property ntxec_battery_properties[] = {
+	POWER_SUPPLY_PROP_VOLTAGE_NOW,
+};
+
+struct ntxec_battery {
+	struct ntxec *ec;
+};
+
+#define NTXEC_REG_READ_BATTERY	0x41
+
+static int ntxec_battery_get_property(struct power_supply *psy,
+				     enum power_supply_property psp,
+				     union power_supply_propval *val)
+{
+	struct ntxec_battery *priv = power_supply_get_drvdata(psy);
+	int ret;
+	unsigned int value;
+
+	switch (psp) {
+		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
+			if (ret < 0)
+				return ret;
+
+			/* ec value to microvolt conversion:
+			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
+			 * with readings 767 to 1023; each increment represents 4687,5uV.
+			 * adjust 3V boundary slightly to report exactly 4.2V when full.
+			 */
+			val->intval = 2999872 + (value - 767) * 4688;
+			break;
+		default:
+			dev_err(&psy->dev, "%s: invalid property %u\n", __func__, psp);
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct power_supply_desc ntxec_battery_desc = {
+	.name = "ec-battery",
+	.type = POWER_SUPPLY_TYPE_BATTERY,
+	.properties = ntxec_battery_properties,
+	.get_property = ntxec_battery_get_property,
+	.num_properties = ARRAY_SIZE(ntxec_battery_properties),
+};
+
+static int ntxec_battery_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ntxec *ec = dev_get_drvdata(dev->parent);
+	struct power_supply_config psy_cfg = {};
+	struct ntxec_battery *priv;
+	struct power_supply *psy;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->ec = ec;
+	psy_cfg.drv_data = priv;
+	psy_cfg.fwnode = dev_fwnode(dev->parent);
+	psy_cfg.no_wakeup_source = true;
+	psy = devm_power_supply_register(dev, &ntxec_battery_desc, &psy_cfg);
+	if (IS_ERR(psy))
+		return PTR_ERR(psy);
+
+	return 0;
+}
+
+static struct platform_driver ntxec_battery_driver = {
+	.driver = {
+		.name = "ntxec-battery",
+	},
+	.probe = ntxec_battery_probe,
+};
+module_platform_driver(ntxec_battery_driver);
+
+MODULE_AUTHOR("Josua Mayer <josua.mayer@jm0.eu>");
+MODULE_DESCRIPTION("Battery driver for Netronix EC");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ntxec-battery");

-- 
2.43.0

Re: [PATCH 3/4] power: supply: add battery driver for netronix ec

[Sebastian Reichel]

[-- Attachment #1: Type: text/plain, Size: 5853 bytes --]

Hi,

On Fri, Jan 02, 2026 at 07:00:32PM +0100, Josua Mayer wrote:
> Implement a simple battery driver for monitoring voltage with the
> netronix embedded controller found in certain ebook readers.
> 
> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
> ---
>  drivers/power/supply/Kconfig         |   9 ++++
>  drivers/power/supply/Makefile        |   1 +
>  drivers/power/supply/ntxec-battery.c | 101 +++++++++++++++++++++++++++++++++++

That's indeed simple :)

>  3 files changed, 111 insertions(+)
> 
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index 92f9f7aae92f..0f944c10e50b 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -1132,4 +1132,13 @@ config FUEL_GAUGE_MM8013
>  	  the state of charge, temperature, cycle count, actual and design
>  	  capacity, etc.
>  
> +config BATTERY_NTXEC
> +	tristate "Battery driver for Netronix embedded controller"
> +	depends on MFD_NTXEC

You can add "|| COMPILE_TEST"

> +	help
> +	  Say yes here to enable netronix ec battery monitoring driver.
> +	  It enables the monitoring battery voltage on certain e-book readers
> +	  using an embedded controller by ODM Netronix. Battery design
> +	  characteristics are read from device-tree if available.
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index 4b79d5abc49a..db6fc815f9da 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
>  obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
>  obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
>  obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
> +obj-$(CONFIG_BATTERY_NTXEC)	+= ntxec-battery.o
> diff --git a/drivers/power/supply/ntxec-battery.c b/drivers/power/supply/ntxec-battery.c
> new file mode 100644
> index 000000000000..f49f0966d18d
> --- /dev/null
> +++ b/drivers/power/supply/ntxec-battery.c
> @@ -0,0 +1,101 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * The Netronix embedded controller is a microcontroller found in some
> + * e-book readers designed by the original design manufacturer Netronix, Inc.
> + * It contains RTC, battery monitoring, system power management, and PWM
> + * functionality.
> + *
> + * This driver implements battery monitoring.
> + *
> + * Copyright 2021 Josua Mayer <josua.mayer@jm0.eu>
> + */
> +
> +#include <linux/mfd/ntxec.h>

^ you probably don't need this with my comments down below :)

> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +
> +static const enum power_supply_property ntxec_battery_properties[] = {
> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
> +};
> +
> +struct ntxec_battery {
> +	struct ntxec *ec;
> +};

Store the regmap instead of the ec. You don't need anything else.

> +#define NTXEC_REG_READ_BATTERY	0x41
> +
> +static int ntxec_battery_get_property(struct power_supply *psy,
> +				     enum power_supply_property psp,
> +				     union power_supply_propval *val)
> +{
> +	struct ntxec_battery *priv = power_supply_get_drvdata(psy);
> +	int ret;
> +	unsigned int value;
> +
> +	switch (psp) {
> +		case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +			ret = regmap_read(priv->ec->regmap, NTXEC_REG_READ_BATTERY, &value);
> +			if (ret < 0)
> +				return ret;
> +
> +			/* ec value to microvolt conversion:
> +			 * vendor kernel source suggests linear behaviour from 3V to 4.2V
> +			 * with readings 767 to 1023; each increment represents 4687,5uV.

4687.5uV ?

> +			 * adjust 3V boundary slightly to report exactly 4.2V when full.
> +			 */
> +			val->intval = 2999872 + (value - 767) * 4688;
> +			break;
> +		default:
> +			dev_err(&psy->dev, "%s: invalid property %u\n", __func__, psp);
> +			return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct power_supply_desc ntxec_battery_desc = {
> +	.name = "ec-battery",
> +	.type = POWER_SUPPLY_TYPE_BATTERY,
> +	.properties = ntxec_battery_properties,
> +	.get_property = ntxec_battery_get_property,
> +	.num_properties = ARRAY_SIZE(ntxec_battery_properties),
> +};
> +
> +static int ntxec_battery_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct ntxec *ec = dev_get_drvdata(dev->parent);

Based on the regmap comment above, I think you can just do the
following and completley avoid 'struct ntxec' (please test):

struct regmap *regmap = dev_get_regmap(dev->parent, NULL);

> +	struct power_supply_config psy_cfg = {};
> +	struct ntxec_battery *priv;
> +	struct power_supply *psy;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->ec = ec;
> +	psy_cfg.drv_data = priv;
> +	psy_cfg.fwnode = dev_fwnode(dev->parent);
> +	psy_cfg.no_wakeup_source = true;
> +	psy = devm_power_supply_register(dev, &ntxec_battery_desc, &psy_cfg);
> +	if (IS_ERR(psy))
> +		return PTR_ERR(psy);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver ntxec_battery_driver = {
> +	.driver = {
> +		.name = "ntxec-battery",
> +	},
> +	.probe = ntxec_battery_probe,
> +};
> +module_platform_driver(ntxec_battery_driver);
> +
> +MODULE_AUTHOR("Josua Mayer <josua.mayer@jm0.eu>");
> +MODULE_DESCRIPTION("Battery driver for Netronix EC");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:ntxec-battery");

I know there are a bunch of wrong examples in my subsystem, but the
proper way to do this is to drop this alias and instead add a
platform_device_id table together with MODULE_DEVICE_TABLE(platform, ...).
See for example cros_peripheral_charger.c

Greetings,

-- Sebastian

[-- Attachment #2: signature.asc --]
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[PATCH 4/4] mfd: ntxec: register battery subdevice.

[Josua Mayer]

Add Netronix EC battery driver as subdevice.

Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
---
 drivers/mfd/ntxec.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
index 08c68de0f01b..d5059b8862aa 100644
--- a/drivers/mfd/ntxec.c
+++ b/drivers/mfd/ntxec.c
@@ -139,6 +139,7 @@ static const struct regmap_config regmap_config = {
 static const struct mfd_cell ntxec_subdev[] = {
 	{ .name = "ntxec-rtc" },
 	{ .name = "ntxec-pwm" },
+	{ .name = "ntxec-battery" },
 };
 
 static const struct mfd_cell ntxec_subdev_pwm[] = {

-- 
2.43.0

Re: [PATCH 0/4] power: supply: add battery driver for netronix ec

[Ing. Josua Mayer]

Greetings everyone,

I made some mistake using "b4" on a different device,
and the v2 was not added as subject prefix.

I will try to fix it after hopefully some comments.

Am Fri, 02 Jan 2026 19:00:29 +0100
schrieb Josua Mayer <josua.mayer@jm0.eu>:

> This series adds a new battery driver for the netronix embedded
> controller multi-function device.
> 
> Bindings are updated supporting a monitored battery, and battery
> description is added to kobo aura device-tree.
> 
> Signed-off-by: Josua Mayer <josua.mayer@jm0.eu>
> ---
> Changes in v2:
> - Fixed identity mixup between from address and SoB.
>   (Reported-by: Krzysztof Kozlowski <krzk@kernel.org>)
> - Changed patch ordering, device-tree first.
> - Separated new driver and mfd subdevice changes into separate
> patches. (Reported-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>)
> - reworded Kconfig to explicitly mention device-tree
>   instead of vague firmware tables expression.
>   (Reported-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>)
> 
> ---
> Josua Mayer (4):
>       dt-bindings: mfd: netronix,ntxec: add reference to power-supply
>       ARM: dts: imx: imx50-kobo-aura: add description for battery
>       power: supply: add battery driver for netronix ec
>       mfd: ntxec: register battery subdevice.
> 
>  .../devicetree/bindings/mfd/netronix,ntxec.yaml    |   9 +-
>  arch/arm/boot/dts/nxp/imx/imx50-kobo-aura.dts      |   9 ++
>  drivers/mfd/ntxec.c                                |   1 +
>  drivers/power/supply/Kconfig                       |   9 ++
>  drivers/power/supply/Makefile                      |   1 +
>  drivers/power/supply/ntxec-battery.c               | 101
> +++++++++++++++++++++ 6 files changed, 127 insertions(+), 3
> deletions(-) ---
> base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> change-id: 20251227-kobo-aura-battery-3e60bc159d16
> 
> Best regards,